After calculation, how is the zakat sum paid?

If the issuing company paid zakat on its business, should there be any payment of zakat by investors?

If the company pays zakat, the shareholders do not need to pay because there is no double payment of zakat.

Is investment in Shariah non-compliant shares subject to zakat?

No, zakat is only applicable to Shariah-compliant assets only. Zakat is also not applicable to gain from disposal as a result of reclassification to Shariah non-compliant; such gain shall be treated in accordance to the SAC SC recommendation.

Is investment in Shariah-compliant shares by non-Muslims subject to zakat?

Zakat is applicable to Muslims only.

Zakat falls under the purview of state religious authorities thus Zakat requirements may differ. For further information on zakat of shares, please refer to the zakat authorities of your respective states.